NAME

       fgetpos, fseek, fsetpos, ftell, rewind - reposition a stream

SYNOPSIS

       #include <stdio.h>

       int fseek(FILE *stream, long offset, int whence);

       long ftell(FILE *stream);

       void rewind(FILE *stream);

       int fgetpos(FILE *stream, fpos_t *pos);

       int fsetpos(FILE *stream, const fpos_t *pos);

DESCRIPTION

       The  fseek()  function  sets  the  file  position indicator for the stream pointed to by stream.  The new
       position, measured in bytes, is obtained by adding offset bytes to the position specified by whence.   If
       whence  is  set  to SEEK_SET, SEEK_CUR, or SEEK_END, the offset is relative to the start of the file, the
       current position indicator, or end-of-file, respectively.  A successful  call  to  the  fseek()  function
       clears  the  end-of-file indicator for the stream and undoes any effects of the ungetc(3) function on the
       same stream.

       The ftell() function obtains the current value of the file position indicator for the stream  pointed  to
       by stream.

       The  rewind()  function  sets  the  file  position  indicator  for the stream pointed to by stream to the
       beginning of the file.  It is equivalent to:

              (void) fseek(stream, 0L, SEEK_SET)

       except that the error indicator for the stream is also cleared (see clearerr(3)).

       The fgetpos() and fsetpos() functions are alternate interfaces equivalent to ftell()  and  fseek()  (with
       whence set to SEEK_SET), setting and storing the current value of the file offset into or from the object
       referenced by pos.  On some non-UNIX systems, an fpos_t object may be a complex object and these routines
       may be the only way to portably reposition a text stream.

RETURN VALUE

       The rewind() function returns no value.  Upon successful completion, fgetpos(), fseek(), fsetpos() return
       0, and ftell() returns the current offset.  Otherwise, -1 is returned and errno is set  to  indicate  the
       error.

ERRORS

       EINVAL The  whence  argument  to fseek() was not SEEK_SET, SEEK_END, or SEEK_CUR.  Or: the resulting file
              offset would be negative.

       ESPIPE The file descriptor underlying stream is not seekable  (e.g.,  it  refers  to  a  pipe,  FIFO,  or
              socket).

       The  functions  fgetpos(),  fseek(),  fsetpos(),  and  ftell() may also fail and set errno for any of the
       errors specified for the routines fflush(3), fstat(2), lseek(2), and malloc(3).

ATTRIBUTES

       For an explanation of the terms used in this section, see attributes(7).

       ┌────────────────────────────┬───────────────┬─────────┐
       │Interface                   │ Attribute     │ Value   │
       ├────────────────────────────┼───────────────┼─────────┤
       │fseek(), ftell(), rewind(), │ Thread safety │ MT-Safe │
       │fgetpos(), fsetpos()        │               │         │
       └────────────────────────────┴───────────────┴─────────┘

CONFORMING TO

       POSIX.1-2001, POSIX.1-2008, C89, C99.

SEE ALSO

       lseek(2), fseeko(3)

COLOPHON

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